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Behind the U.L. LabelAugust 1955 Popular
Electronics

August 1955 Popular Electronics

[Table of Contents]People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.

The Underwriter's
Laboratory (UL) is an entity that seems to have been around forever. A lot of people - maybe most people - assume
that it is a government entity. In fact, it is a non-profit organization sponsored by the National Board of Fire
Underwriters. Its roots are traceable back to the Chicago World's Fair in 1893. Concern over the potential fire
hazard of Edison's light bulbs was the impetus for the effort. Another aspect of the UL that a lot of people don't
know is that the UL label of approval is no guarantee that the device works properly, only that is passes
standards of safety as it relates to fire hazards. This article in the August 1955 edition of Popular Electronics
gives a brief history.

Behind the U.L.
Label

Equipment is tested, dropped, pounded, and burned before it is rated as safe and tagged with
the Underwriters' okay.

A familiar sight on much electrical and electronic equipment used
today is an Underwriters' Laboratories label. Exactly what is implied by the use of this label, however, is often
misunderstood.

Underwriters' Laboratories, Inc. is a non-profit organization sponsored by the National
Board of Fire Underwriters. Its function is to test and inspect materials and equipment to prevent loss of life
and property from fire, crime and casualty hazards. To do this adequately, it subjects devices to grueling tests.
Only the hardiest designs survive and earn the right to the coveted label of acceptance.

Television sets are subjected to a thorough going-over by Underwriters' Laboratories. Inc. engineers. Special
attention is paid to shock hazards and to overheating problems. Cabinets are pounded and safety glass hit with
steel balls in test.

An enclosed heavy-duty switch is tested in one of U.L.'s many laboratories. Equipment such as this is operated
repeatedly under excessive loads before it is approved and given the U.L. label.

Automatic flatiron is dropped four times during continuous operation test of 500 hours. Temperatures of various
parts as well as operation of the thermostat are also checked.

These are only a few of the authorized labels used by U.L. to designate approved equipment. An item bearing such
a label has met specifications and passed severe tests.

It is important to point out that U. L.
approval does not guarantee quality of performance. The testing is concerned primarily with the safety aspects of
equipment. Thus, the label on an approved radio receiver, for instance, does not imply that it will perform better
than one not so approved. It does mean, though, that the chance of setting a house on fire is negligible if the
approved model is used.

No conceivable method of testing is overlooked. Much of the test equipment is of
U. L.'s own design and they dream up diabolical plans to subject samples to the meanest treatment possible. They
try to anticipate all of the mistakes that could be made by a consumer. Appliances are left on for weeks and
electric heater cords are twisted and untwisted thousands of times.

Television cabinets get a thorough
pounding before they receive U. L. approval. A large picture tube can be a deadly weapon when broken, as it hurls
tiny fragments of glass in all directions. To insure against injury, the safety screen on the front must be
capable of withstanding such shattering. A pound-and-a­quarter steel ball is hurled at the set to determine its
fitness for this purpose.

Electronic equipment is often used by U.L. technicians. Here, the split-second
operation of a burglary detection system is photographed. Accuracy is assured by using a cathode-ray oscilloscope,
a beat­frequency generator, and various meters.

To determine whether a safe is fire­proof and
burglar-proof, U. L. employs its own staff of "arsonists" and "safecrackers." These men are masters at their
trades and tackle a new item with drills, sledges, torches, and explosives. Just to make sure, the safes are
dropped onto concrete from a second-story level, then placed in a 2000° F furnace for an hour or so. If the
internal temperature goes high enough to turn valuable papers brown, what is left of the safe is returned to the
maker with regrets.

Fire doors are tested in large gas furnaces where flames lick at them until they are
red-hot. Then a fire hose is intermittently played on the other side of the door. Acceptable fire barriers must
pass the fire endurance as well as the hose stream tests.

U. L.'s Growth

The organization had its unique start when bulbs were installed at the
first Chicago World's Fair in 1893. These became the Fair's chief attraction - as well as its greatest hazard.
Fires, started by the not-yet-perfected lamps and wiring, were commonplace. This led a group of New England
insurance interests to authorize William H. Merrill, a young engineer, to investigate the situation. He responded
to each fire alarm at the fairgrounds. If the cause were electrical, he would try to locate the defective device
and determine why it failed.

Because of Merrill's insistence on thorough testing before the lamps were
installed, and correcting their faults before offering them to the public, Underwriters' Laboratories, Inc. was
born the following year. Merrill was its first president.

Since then, U. L. has mushroomed. Over 375,000
products have been found acceptable under its rigorous standards. Testing laboratories are located in Chicago, New
York and San Francisco, with representatives in nearly 200 cities insuring that the standards are upheld at the
factories. The work is financed solely by charges made to manufacturers for the inspection of their equipment.

Annual lists are published giving the manufacturers' names and their approved products. Four main lists are
prepared which cover: electrical equipment; fire protection equipment; gas, oil and miscellaneous appliances; and
accident hazard, automotive equipment and burglary protection.

Good will and impeccable honesty is the
main stock-in-trade of this organization. U. L. never solicits business, but industry has learned that it is well
worth the effort to make sure its products deserve the U. L. label.